Field of the Disclosure
Embodiments of the present invention relate to a flat panel display (FPD) device. More particularly, the embodiments relate to an organic light emitting display device including a thin film transistor (TFT).
Discussion of the Related Art
Because of advantages such as a thin profile, lighting thereof and low power consumption, flat panel display devices are widely used. In the flat panel display devices, a liquid crystal display (LCD) device and an organic light emitting display device including a thin film transistor (TFT) are good in resolution, color display, and image quality, and thus are commercialized as display devices for notebook computers, tablet computers, and desktop computers. In particular, the organic light emitting display device has a fast response time and low power consumption, and have no limitation in a viewing angle because the organic light emitting display device is a self-emitting light. Accordingly, the organic light emitting display device is attracting much attention as next generation FPD devices.
A general organic light emitting display device includes a display panel including a plurality of pixels and a panel driver that emits light from each of the plurality of pixels. Here, the plurality of pixels are respectively formed in a plurality of pixel areas defined by intersections between a plurality of data lines and a plurality of gate lines.
Each of the plurality of pixels, as illustrated in FIG. 1, includes a switching transistor Tsw, a driving transistor Tdr, a capacitor Cst, and an organic light emitting element OLED.
The switching transistor Tsw is turned on according to a gate signal GS supplied to a gate lines GL, and supplies a data voltage Vdata, supplied to a data line DL, to the driving transistor Tdr.
The driving transistor Tdr is turned on with the data voltage Vdata supplied from the switching transistor Tsw, and controls a data current Ioled flowing to the organic light emitting element OLED with a driving voltage VDD.
The capacitor Cst is connected between a gate and source of the driving transistor Tdr, stores a voltage corresponding to the data voltage Vdata supplied to the gate of the driving transistor Tdr, and turns on the driving transistor Tdr with the stored voltage.
The organic light emitting element OLED is electrically connected between the source of the driving transistor Tdr and a cathode electrode receiving a cathode voltage VSS, and emits light with the data current Ioled supplied from the driving transistor Tdr.
Each pixel of the general organic light emitting display device controls a level of the data current Ioled, which flows to the light emitting element OLED with the driving voltage VDD, with a switching time of the driving transistor Tdr based on the data voltage Vdata to emit light from the light emitting element OLED, thereby displaying an image.
However, in the general organic light emitting display device, due to a non-uniformity of a manufacturing process of a thin film transistor (TFT), a threshold voltage “Vth” of each of the transistors Tdr and Tsw (particularly, the driving transistor Tdr) is shown differently for each pixel. Therefore, in the general organic light emitting display device, the reliability of the TFT and display panel is reduced due to the initial scattering or sequential shift of a threshold voltage of the TFT included in each pixel.